Products for use in low temperature fluxless brazing

Abstract

A brazing product for low temperature fluxless brazing comprises a filler metal-forming composition which melts in the range from about 380-575° C. The filler metal-forming composition comprises zinc optionally in combination with aluminum and/or silicon, and further comprises at least one braze promoter selected from nickel, cobalt, iron and palladium. The filler metal-forming composition may comprise a single layer or may comprise a number of distinct layers. The brazing product may take the form of a brazing preform or a brazing sheet or casting in which the filler metal-forming composition is deposited on a non-consumable substrate. The substrate may preferably comprise aluminum or an aluminum alloy, but may instead be comprised of one or more metals other than aluminum.

What is claimed is: 
     
       1. A brazing product for fluxless brazing comprising a filler metal-forming composition comprised of a plurality of layers, including:
 (a) at least one temperature modifier layer, wherein said at least one temperature modifier layer has an overall zinc content of about 25-100% by weight of the at least one temperature modifier layer, an overall aluminum content of up to about 65% by weight of the temperature modifier layer, and an overall silicon content of up to about 18% by weight of the temperature modifier layer; and 
 (b) at least one braze-promoting layer, wherein said at least one braze-promoting layer comprises at least one braze-promoting metal selected from nickel, cobalt, iron and palladium; 
 wherein the filler metal-forming composition melts completely at a braze temperature in the range of about 380-575° C.; 
 wherein said at least one braze-promoting layer comprises said at least one braze-promoting metal in an amount of from about 1-10% by weight of the filler metal-forming composition; and 
 wherein said at least one temperature modifier layer comprises zinc in an amount of about 25-99% by weight of the filler metal-forming composition, aluminum in an amount of up to about 65% by weight of the filler metal-forming composition, and silicon in an amount of up to about 18% by weight of the filler metal-forming composition. 
 
     
     
       2. The brazing product of  claim 1 , wherein the at least one temperature modifier layer has an overall zinc content of at least 50% by weight of the at least one temperature modifier layer. 
     
     
       3. The brazing product of  claim 1 , wherein the at least one temperature modifier layer has an overall zinc content of at least 90% by weight of the at least one temperature modifier layer. 
     
     
       4. The brazing product of  claim 1 , wherein the braze-promoting metal comprises nickel, optionally in combination with lead and/or bismuth. 
     
     
       5. The brazing product of  claim 4 , wherein the at least one braze-promoting metal is nickel which is present in the braze-promoting layer in an amount of about 1-4% by weight of the filler metal-forming composition. 
     
     
       6. The brazing product of  claim 1 , wherein the filler metal-forming composition has a liquidus temperature in the range of about 380-575° C. 
     
     
       7. The brazing product of  claim 1 , wherein the filler metal-forming composition has a liquidus temperature in the range of about 400-570° C. 
     
     
       8. The brazing product of  claim 1 , comprising a brazing preform. 
     
     
       9. The brazing product of  claim 1 , further comprising a non-consumable substrate having at least one surface on which the filler metal-forming composition is provided, the substrate having a solidus temperature greater than 575° C. 
     
     
       10. The brazing product of  claim 9 , wherein the substrate comprises one or more of aluminum, aluminum alloys, copper, copper alloys, titanium, titanium alloys, nickel, nickel alloys, and steels. 
     
     
       11. The brazing product of  claim 10 , wherein the substrate comprises aluminum or an aluminum alloy. 
     
     
       12. The brazing product of  claim 11 , wherein the substrate comprises an aluminum alloy selected from the group consisting of AA1xxx, AA2xxx, AA3xxx, AA5xxx, AA6xxx, AA7xxx and AA8xxx-series alloys and aluminum casting alloys. 
     
     
       13. The brazing product of  claim 12 , comprising an aluminum brazing sheet or an aluminum casting clad with said filler metal-forming composition. 
     
     
       14. The brazing product of  claim 12 , wherein the substrate comprises a cast structure comprised of an aluminum casting alloy, and wherein the casting alloy comprises up to about 8% by weight magnesium. 
     
     
       15. The brazing product of  claim 10 , wherein the substrate comprises a copper alloy selected from the group consisting of brass and bronze. 
     
     
       16. The brazing product of  claim 10 , wherein the substrate comprises a steel selected from the group consisting of high strength steel, low carbon steel, stainless steel, and nickel alloy steel. 
     
     
       17. The brazing product of  claim 16 , wherein the steel is plated or coated with aluminum or copper. 
     
     
       18. The brazing product of  claim 10 , wherein the substrate comprises titanium or a titanium alloy, wherein the filler metal-forming composition includes a bonding layer comprised of nickel, nickel-lead or nickel-bismuth applied directly to the substrate. 
     
     
       19. The brazing product of  claim 18 , wherein the substrate comprises a titanium or titanium alloy mesh. 
     
     
       20. The brazing product of  claim 1 , wherein the at least one temperature modifier layer consists of a single temperature modifier layer having a zinc content from about 90-100% by weight, and wherein the at least one braze-promoting layer comprises nickel. 
     
     
       21. The brazing product of  claim 20 , wherein the at least one braze-promoting layer comprises nickel in combination with lead and/or bismuth. 
     
     
       22. The brazing product of  claim 1 , comprising a brazing preform, wherein the preform has a core comprised of said at least one temperature modifier layer, and wherein the core has a surface on which one of said at least one braze-promoting layer is provided. 
     
     
       23. The brazing product of  claim 1 , further comprising a non-consumable substrate having at least one surface on which the at least one temperature modifier layer is provided, wherein the substrate has a solidus temperature greater than 575° C. and wherein one said at least one braze-promoting layer is provided on top of the at least one temperature modifier layer. 
     
     
       24. The brazing product of  claim 23 , wherein the substrate comprises aluminum or an aluminum alloy. 
     
     
       25. The brazing product of  claim 24 , comprising an aluminum brazing sheet or an aluminum casting clad with said filler metal-forming composition. 
     
     
       26. The brazing product of  claim 24 , wherein another of said braze-promoting layers is provided directly under the temperature modifier layer. 
     
     
       27. The brazing product of  claim 24 , further comprising a bonding layer applied directly to the substrate, wherein the bonding layer is comprised of one or more metals selected from the group consisting of zinc, tin, lead, bismuth, nickel, antimony, magnesium, lithium and thallium. 
     
     
       28. The brazing product of  claim 24 , wherein the brazing product comprises a brazing sheet in which the substrate comprises aluminum or an aluminum alloy, and wherein the substrate is provided with at least the following two temperature modifier layers:
 a first temperature modifier layer applied directly to the substrate and comprised of an aluminum-silicon brazing alloy having a liquidus temperature greater than 575° C.; and 
 a second temperature modifier layer provided on the first temperature modifier layer and comprising at least 90% by weight zinc. 
 
     
     
       29. A brazing product comprising a filler metal-forming composition comprised of one layer, the composition comprising aluminum, silicon and nickels wherein the filler metal-forming composition comprises:
 (a) aluminum in an amount of about 50 to 70% by weight; 
 (b) silicon in an amount of about 11 to 17% by weight; and 
 (c) nickel in an amount of about 13 to 33% by weight. 
 
     
     
       30. The brazing product of  claim 29 , further comprising a non-consumable substrate having at least one surface on which the filler metal-forming composition is provided, the substrate having a solidus temperature greater than 575° C. 
     
     
       31. The brazing product of  claim 30 , wherein the substrate comprises aluminum or an aluminum alloy. 
     
     
       32. A brazing product for fluxless brazing comprising a filler metal-forming composition consisting of a single layer, said filler metal-forming composition is formed by roll compacting a mixture of powder metals, comprising:
 (a) zinc in an amount of about 25-99% by weight; 
 (b) aluminum in an amount of up to about 65% by weight; 
 (c) silicon in an amount of up to about 18% by weight; 
 (d) a braze-promoting metal in amount of from about 1-10% by weight, wherein the braze-promoting metal comprises one of more metals selected from the group consisting of nickel, cobalt, iron and palladium. 
 
     
     
       33. The brazing product of  claim 32 , wherein the filler metal-forming composition comprises zinc and nickel. 
     
     
       34. The brazing product of  claim 32 , wherein the filler metal-forming layer further comprises a poly(alkylene carbonate) binder. 
     
     
       35. The brazing product of  claim 34 , wherein the binder is a poly(propylene carbonate). 
     
     
       36. The brazing product of  claim 34 , wherein the binder comprises up to about 10 by weight of the filler metal-forming composition. 
     
     
       37. The brazing product of  claim 32 , comprising a brazing preform. 
     
     
       38. A brazing product for fluxless brazing comprising a filler metal-forming composition comprised of one or more layers, the composition comprising:
 (a) zinc in an amount of about 50-99% by weight; 
 (b) aluminum in an amount of up to about 65% by weight; 
 (c) silicon in an amount of up to about 18% by weight; 
 (d) an amount of from about 1-10% by weight of at least one braze-promoting metal selected from nickel, cobalt, iron and palladium; 
 wherein the filler metal-forming composition melts completely at a braze temperature in the range of about 380-575° C. 
 
     
     
       39. The brazing product of  claim 38 , wherein the zinc content of the filler metal-forming composition is at least 90% by weight.